The invention disclosed and claimed herein is generally directed to an improved catheter for implantation in a patient or other subject More particularly, the invention pertains to a catheter of such type which significantly simplifies the implantation procedure. Even more particularly, the invention pertains to a catheter of such type, wherein a bend of virtually any angle can be readily formed in the catheter, at any position along the length thereof.
As is well known, a shunt or shunt system can be implanted in a patient, in order to remove excess cerebrospinal fluid (CSF) from the patient's brain. The shunt system generally includes a ventricular catheter, comprising a thin tubular structure, which is inserted into a brain ventricle to provide a passage or channel for fluid flow. An implanted catheter usually must be able to remain in the brain on a long term or permanent basis, and is typically formed of pliable or resilient material such as silicone. In a common procedure for implanting a ventricular catheter, the surgeon bores a hole, sufficient to accommodate the catheter diameter, through the wall of the patient's skull. The catheter is then inserted through the hole by means of a stylet or the like. It is generally necessary to form or otherwise provide a bend in the catheter, proximate to the hole, so that the catheter portion extending out of the hole will lie along the patient's head. Such catheter portion can then be connected to a shunt valve or other component of the shunt system. Clearly, it is essential to avoid, as much as possible, traumatizing surrounding brain tissue during this procedure.
The bend which must be formed in the catheter will generally be of a fairly sharp angle, and lie in a range which may be on the order of 45.degree.-90.degree.. Since the catheter is formed of soft, pliable silicone, an angled bend of such magnitude could pinch or crimp the catheter and seriously obstruct fluid flow. To prevent such obstruction, a surgeon is provided with a set of different ventricular catheters, each having a specified angle preformed therein, at a specified distance from the proximal or forward end of the catheter. For example, some catheters in the set will have bends preformed therein at angles of 90.degree., and other catheters will have bends preformed therein at angles of 45.degree.. The angled bends are located at standard distances from the proximal end of the catheter, such as at 5 centimeters, 7 centimeters and 9 centimeters therefrom. Such dimension is referred to herein as catheter insertion length. For a given implant operation, the neurosurgeon will select the catheter having the respective dimensions which he feels are most suited to a particular patient.
Unfortunately, with the present state of the art it may not be possible to accurately determine, in advance, the depth of insertion required for a catheter, in order to reach a particular ventricle. As a result, the insertion length of the catheter selected for use may be too long or too short. However, such deficiency will not become apparent until after the catheter has been inserted into a patient's brain. Since there is no way to adjust the location of a preformed bend along the length of a catheter, the inserted catheter must be withdrawn, and then replaced by another catheter having a longer or shorter insertion length, as required. It will be readily appreciated that withdrawal of the first catheter, followed by insertion of a second catheter, can significantly increase the trauma experienced by brain tissue proximate to the region of insertion. Moreover, since a surgeon using catheters with preformed bends is limited to standard sizes, both for bend angle and insertion length, he may not be able to fit a catheter to a patient as accurately as he would like.
An alternative prior art approach for providing a bend in a ventricular catheter is exemplified by U.S. Pat. No. 4,435,174, issued Mar. 6, 1984 to Redmond et al. Such patent is directed to structure for smoothly guiding a catheter around an arc, to provide bends of 90.degree. or other prespecified angle. Such guides generally require stitches to affix them to a patient's scalp. Thus, additional steps are added to the shunt implantation procedure. Moreover, such guides once again have the disadvantage described above, i.e., they limit a surgeon to catheter bend angles of fixed standard sizes.
In view of the above drawbacks and disadvantages of the prior art, it would be desirable to provide an arrangement for forming a bend of any selected angle in a catheter, at any position along the length thereof. Moreover, the forward or proximal end of a conventional catheter, when inserted into a brain ventricle, may droop toward the floor or bottom thereof. This tends to bring the catheter drainage holes, through which CSF must pass, into contact with a substance known as chorid plexus. Such substance comprises fine strands or filaments, which can plug or clog the catheter drainage holes. Accordingly, it would be further desirable to provide rigidity to the proximal end of a catheter, to support it upwardly in the ventricle and away from the chorid plexus. Moreover, in an arrangement for a ventricular catheter, it is essential to avoid any projections, angles, or comers in the catheter outer surface. Any such projections or the like could tear or otherwise harm the surrounding brain tissue. It is particularly important to avoid such projections where the catheter is to remain in contact with delicate brain tissue for a long period of time. It is also essential to ensure that no hard internal component of the catheter, over the long period, is ever able to break or rupture through the smooth outer surface thereof.